The present invention relates to the magnetic resonance arts. It finds particular application in conjunction with magnetic resonance imaging systems for imaging portions of a patient in a surgical site and will be described with particular reference thereto. However, it is to be appreciated that the present invention will also find application in conventional imaging, spectroscopy, combined spectroscopic and imaging applications, and the like.
Heretofore, magnetic resonance imaging systems have surrounded the subject with relatively large and bulky equipment. High field magnetic resonance imaging systems typically receive the patient within a long bore with the imaging region at the geometric center of the bore. Access for surgical procedures is limited at best.
"Open" magnet systems, such as magnetic resonance imaging systems with "C" magnets, provide better physician access. However, large diameter pole pieces are positioned immediately above and below the region of interest of the patent. Typically, the pole pieces have a diameter on the order of 1.5-3 times the space between them for receiving the patient. Reaching into this narrow gap is sufficiently awkward that the patient is typically moved into the bore for imaging and out of the bore for the surgical procedure. Because a patient undergoing surgery is typically interconnected with a plurality of monitors, electrical leads, tubes, intravenous and intra-arterial injections, and the like, moving the patient is considered highly undesirable.
To provide better surgical access, proposals have been made in which the magnet and ferrous flux path structure are enlarged to the size of a small room. To minimize magnetic flux losses, the room is typically small with a low ceiling. The main magnet is positioned low which limits head room, often closely adjacent the region of interest which is typically coincident with the surgeon's work area. Although providing improved access to the patient, these rooms still have drawbacks. The ferrous panels of the flux return path in the ceiling, walls, and floor are heavy. The rooms tend to be claustrophobic. Moreover, the magnet and associate structures still limit surgical access to the region of concern.
The present invention provides a new and improved method and apparatus which overcomes the above-referenced problems and others.